Antimicrobics Acting on the Outer and Cytoplasmic Membranes
The polypeptide antimicrobics polymyxin B and colistin have a cationic detergent-like effect. They bind to the cell membranes of susceptible Gram-negative bacteria and alter their permeability, resulting in loss of essential cytoplasmic components and bacterial death. These agents react to a lesser extent with cell membranes of the host, resulting in nephrotoxicity and neurotoxicity. Their spectrum is essentially Gram-negative; they act against P. aeruginosa and other Gram-negative rods. Although these antimicrobics were used for systemic treatment in the past, their use is now limited to topical applications. They have an advantage; resistance to them rarely develops.